Costs: GainLife updated syntax

Hi, I've commited r19122 which among other things replaces cost syntaxes "OthersEachGainLife" and "OppGainLife" with a more unversal model:
Selector gets passed to the method isValid() of each player in game (use same syntax as for target selection here, eg: Player.Other). Matching players are considered valid targets.
M - number of players to apply cost to. Can be either a number or asterisk (*) meaning ALL players matching the selector. If omitted, M defaults to 1.
- Code: Select all
GainLife<N/Selector/M>
Selector gets passed to the method isValid() of each player in game (use same syntax as for target selection here, eg: Player.Other). Matching players are considered valid targets.
M - number of players to apply cost to. Can be either a number or asterisk (*) meaning ALL players matching the selector. If omitted, M defaults to 1.